1. Field of the Invention
The present invention relates generally to vehicle brake system and more particularly to vehicle brake system having an anti-skid control apparatus therein.
2. Description of the Prior Art
Recently, an anti-skid control apparatus which can be varied at least into two steps, namely, the low and high speeds of increasing pressure, in order to improve its performance, is being developed. However, it takes generally more time for controlling the anti-skid control apparatus at the low speed of increasing pressure than at the high speed of increasing pressure in this anti-skid control apparatus, so that it is general that the state of low speed of increasing pressure is maintained normally in the non-actuating state of an orifice valve in order to improve the durability of a solenoid and to simplify the structure of the orifice valve. When the braking force is not required and a break pedal is released by a vehicle driver, for example, during anti-skid actuation, i.e., during interrupting state of communication between a master cylinder and a wheel cylinder, the anti-skid actuation is going to return to its non-actuating state. However, in this state the low speed of increasing pressure is maintained as above-mentioned, therefore, a few seconds are necessary to return to the non-actuating state of the anti-skid control apparatus. Accordingly, the remaining pressure according to the spring force of a cut off valve of an actuator is generated at the side of the wheel cylinder during this returning state of the anti-skid control apparatus and the braking force is not able to release. The cut off valve of the actuator is cut off and the fluid pressure is not rapidly supplied from the master cylinder to the wheel cylinder, even when the braking force is again required during the returning state, namely, during the non-actuating state of the anti-skid control apparatus.